Lopping shears having a pair of elongated members disposed for cooperative engagement about a pivotable joint are widely used. Each of such members generally comprises a jaw, typically made of stamped or forged metal or other suitable material, having an opposed force-applying end connected to a handle. In anvil-type loppers, one of the jaws is formed as a blade while the other jaw is configured as an anvil.
Shearing heavy growth such as tree limbs on the order of two inches in diameter requires considerable force. To provide additional leverage, lopping shears are often provided with extra long handles. Such configuration gives the user the extra leverage required to perform the desired cutting operation, and the extended reach to trim distant tree branches and the like. Although these handles have often been made of wood, to reduce forearm fatigue, more recent prior art loppers have included hollow handles made of fiberglass or other suitable material, as disclosed in U.S. Pat. No. 5,570,510 naming the present inventor.
However, in certain cases some of these prior art loppers may still be relatively awkward to manipulate, particularly in areas heavily congested by branches of trees or plants to reach a limb to be trimmed. This is because this congestion typically prevents the user from opening the handles as needed to place the blades (or the blade and anvil) about the heavy growth to be severed. In addition, the various components of these prior art loppers, which are typically exposed, are also prone to getting caught in dense foliage areas.
Some of these constraints have already been recognized and addressed by those skilled in the art. U.S. Pat. No. 5,020,222 to Gosselin discloses a compound action lopper in which an additional lever member connected to one of the jaws increases the cutting force transmitted to the jaws, thereby facilitating the cutting operation. Additional leverage is also provided by a device conceived by the present inventor and disclosed in pending U.S. patent application Ser. No. 08/702,122 filed Aug. 20, 1996.
As illustrated in FIG. 1A, those skilled in the tree trimming art have recognized that the resistance to cutting designated as F presented by a generally round, fibrous growth, such as for example a tree limb L, is not uniform but varies as a function of the penetration of the cutting blade B into the growth. The maximum resistance is typically reached at a point P approximately sixty percent through the cutting stroke. This is because, up to that point, the penetrating action of blade B into limb L results in the compression of an increasing number of fibers as blade B penetrates further into limb L, thereby increasing the density of limb L. As shown in FIG. 1, C represents the region of compression of the fibers of limb L, while F, represents the friction forces opposing the cutting force applied by a user. Beyond point P which is the point of maximum compression of the fibers, the resistance to the cutting action decreases as the blade begins cutting the fibers (illustrated as region S, where the growth begins being severed and, as a result, the resistance to the cutting action subsides until limb L is entirely severed). It therefore becomes advantageous for a cutting tool to be provided with a variable force mechanism that provides maximum leverage at the point in the cutting stroke corresponding to the maximum resistance to cutting.
While loppers of the type described in the foregoing suitably provide the additional leverage desired to perform the desired cutting function, it can be readily appreciated that in certain cases their use may still be rendered difficult by the heavy foliage surrounding a limb to be trimmed. Accordingly, it appears desirable to provide a lopper that can alleviate the problems associated with conventional items of that kind, i.e., which is more compact in use so as to facilitate certain trimming operations.